Jamie McIntyre on the A-Day strikes

WASHINGTON (CNN) --Jamie McIntyre, CNN senior Pentagon correspondent, describes how the United States made the decision to launch the A-Day strikes on Baghdad:

MCINTYRE: Gen. Tommy Franks, Central Command commander, was given essentially a 48-hour window to launch this attack at his discretion, based on the conditions he saw at the ground, when he felt the timing would be absolutely right. So it was left to him, within a window of 48 hours.

The start of the war was originally designed to be an air campaign, followed quickly by a ground assault. That was reversed, based in part for concern for the oil fields, the desire to get those troops in on the ground and secure the oil field in the south and prevent a disaster there.

That was one of the factors that switched the timing. Obviously, the impromptu target of opportunity that occurred on the first night was another factor that adjusted the timing of the start of the campaign.

What we saw Friday afternoon was massive explosions in Baghdad. The Pentagon nicknamed this attack "shock and awe," but the technical name for it is "combined effect operations."

It's a very sophisticated, coordinated campaign to hit a series of targets in a specific order, in specific places, designed to greatly magnify the effect this bombing campaign would have, as opposed to a more indiscriminate campaign.